Ankle-Foot Orthosis

ABSTRACT

A preferred embodiment of the invention provides an ankle-foot orthosis ( 1 ) for resisting plantarflexion of a patient&#39;s foot, comprising: a resiliently flexible sock-like orthotic structure ( 10 ) formed of first ( 12 ) and second ( 14 ) tubular sections set at an angle to one another, wherein the second tubular section is capable of being opened for insertion of the patient&#39;s foot and lower leg into respective ones of said first and second tubular sections, the orthosis further comprising at least one closure member ( 34 ) that can be passed round at least part of the periphery of the second tubular section and secured in place to urge the second tubular section towards a closed position in which the second tubular section is closely fitted to the lower leg of the patient.

This invention relates to ankle-foot orthoses.

Orthoses are mechanical devices which impose forces upon a limb of apatient and which can be used for a variety of different purposes. Forexample, orthoses can be provided for supportive, functional, correctiveor protective purposes, or indeed for a combination of these.

Ankle-foot orthoses are typically used to provide protection to theankle and foot of a patient as well as to provide support againstexcessive plantarflexion, or “foot-drop” as it is more colloquiallyknown. Foot plantarflexion is a medical condition that results fromdisease, trauma or congenital abnormality. Patients affected by thecondition typically experience difficulty in walking as their feet tendto drop when lifted off the ground, and to avoid stumbling theytypically have to lift their foot higher than they would otherwise haveto. It is also not atypical for patients to have problems during theswing-through phase of their gait cycle, as a typical sufferer will tendalso to exhibit poor, or impaired, dorsiflexion.

The primary function of an ankle-foot orthosis is to provide aresistance to plantarflexion which helps keep the patient's foot in thecorrect position when the foot is lifted off the ground. As well as thisresistive function, a good ankle-foot orthosis should also provide adegree of assistance to dorsiflexion during the swing-through phase ofthe patient's gait.

A variety of different ankle-foot orthoses have previously been proposedfor resisting plantarflexion, and in some cases for additionallyassisting dorsiflexion.

One previously proposed device is commonly known in the art as an “underfoot” orthosis. As this colloquial name suggests, the orthosis fitsunder the foot, and in this case outside of a shoe. This particulardevice cannot be worn without a shoe, and as such the shoe is anintegral component of the orthosis. The orthosis comprises a pair ofsupporting metal rods, one connected to either side of the shoe in theregion of the heel by means of a plantarflexion stop that preventsfurther foot drop. The upper ends of the rods are connected to asupporting band which is secured about the calf of a patient.

Another previously proposed “under foot” orthosis (which must also beused with a shoe) comprises a rigid one-piece plastics moulding composedof integral sole-abutting and calf-abutting regions. The top of thecalf-abutting region is provided with a closure mechanism that enablesthe device to be secured to the calf of a patient, and the sole abuttingregion acts in conjunction with the shoe to support the foot of thepatient.

Another previously proposed device is known colloquially as an “overfoot” orthosis, meaning that the orthosis fits over the front (dorsal)aspect of the foot, rather than under it as in the abovementionedpreviously proposed devices. This “over foot” orthosis comprises a rigidplastics shell which is worn up against the shin, and which is securedaround the calf by means of an appropriate securing band. The orthosisincludes a stirrup which fits over the foot in the region of the instepto provide the patient with a resistance to plantarflexion.

All of the aforementioned orthoses provide the patient with a devicewhich is capable of resisting plantarflexion. However, it is also thecase that each of them has a number of attendant disadvantages.

To alleviate these problems, we have previously provided (see granted UKPatent No. 2330309) a sock-like structure which is formed of aresiliently flexible material—such as silicone for example. Thesock-like structure, by virtue of the inherent resilience of thematerial from which it is made, provides a resistance to plantarflexionand also stores energy which can subsequently be released to assistdorsiflexion. The orthosis can be coloured to mimic the colour of thepatient's skin (and as such is cosmetically pleasing), can comfortablybe worn in a normal off-the-shelf shoe, and need not be worn with a shoein order to provide a beneficial effect.

The part of the sock-like structure which envelops the patient's ankleand lower leg in use includes an opening (to permit the user to put onthe device), and in the preferred arrangement the opening is closed (tosecure the orthosis in place on the foot of a patient) by means ofrespective parts of a mechanical hook and loop closure (such as velcro®)which are embedded in the sock-like structure. Typically, one part ofthe closure is provided on the outside of the orthosis adjacent one sideof the opening and the other part is provided on the inside surface of atab extending from the other side of the opening, the closure on the tabbeing attachable to the closure adjacent the one side of the opening toclose the opening, and secure the orthosis in place.

Our previous orthosis represented a quantum leap in the field andalleviated most (if not all) of the disadvantages mentioned above (thebulk of which had long been associated with previously proposeddevices), and has proved to be extremely commercially successful.Despite this it is still more expensive to manufacture (and hence moreexpensive for patients to purchase) than we would otherwise like.

One particular problem we have noted in this regard is that it isdifficult to embed the respective parts of the velcro® closure in thesilicone sock-like structure, and that once embedded the closures cansometimes come away from the sock-like structure thereby causing thedevice to fail. These problems tend to lengthen the time taken to makeany one device, and to reduce the yield of the production process as awhole. The effect of this is, ultimately, to make the orthoses moreexpensive to make, and hence more expensive to purchase, than theyotherwise would be.

It is an aim of the present invention to provide an orthosis whichavoids, or at least alleviates, these problems. In particular, it is anaim of the invention to provide an orthosis which can more easily bemanufactured and hence can be manufactured (and ultimately sold) forless.

In pursuit of the above mentioned aims, a presently preferred embodimentof the invention provides an ankle-foot orthosis comprising: a sock-likestructure formed of first and second tubular sections set at an angle toone another, wherein the second tubular section is capable of beingopened for insertion of the patient's foot and lower leg into respectiveones of said first and second tubular sections, the orthosis furthercomprising a closure member that can be passed round at least part ofthe periphery of the second tubular section and secured in place to urgethe second tubular section towards a closed position in which the secondtubular section is closely fitted to the lower leg of the patient.

The principal advantages of this orthosis over that which we previouslyproposed, is that it can be manufactured more quickly (albeit at thecost of a slight reduction in its aesthetic appearance), and with fewerfailures. By reducing the time taken to make any one given orthosis andthe number of failed devices, it is possible to significantly increasethe yield of the manufacturing process and hence to reduce themanufacturing cost (and ultimately the sale price) of each of theorthoses. In tests we have found that the manufacturing time for anorthosis as described herein can be reduced by approximately 40 percentas compared to the manufacturing time for an orthosis as described inour previous GB patent. This reduction in manufacturing time allows usto sell orthoses of the type described herein for about half the priceof orthoses of the type described in our earlier GB patent.

In a highly preferred embodiment, the closure member is located outsideof the periphery of the second tubular section when the second tubularsection is in the aforementioned closed position.

Further objects, features and advantages of embodiments of the presentinvention will be apparent from the detailed description that follows.

Various preferred embodiments of the invention will now be described, byway of illustrative example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic front perspective view of an orthosis inaccordance with a preferred embodiment of the present invention in aclosed configuration;

FIG. 2 is a rear perspective view of the orthosis depicted in FIG. 1;

FIG. 3 is a side elevation of the orthosis depicted in FIGS. 1 and 2;

FIG. 4 is a rear perspective view of the orthosis depicted in FIG. 1 inan open configuration; and

FIG. 5 is a rear perspective view of the orthosis depicted in FIG. 4 ina partly closed configuration.

FIG. 6 is a schematic front perspective view of an orthosis inaccordance with a second embodiment of the invention;

FIG. 7 is a schematic side view of an orthosis in accordance with athird embodiment of the invention; and

FIG. 8 is a schematic side view of an orthosis in accordance with afourth embodiment of the invention.

FIG. 1 is a perspective view of an embodiment of the invention in aclosed configuration. The orthosis 1 depicted in FIG. 1 is shown as itwould appear when worn by a patient (the patient's foot, ankle and lowerleg having been omitted for clarity), although it worth noting that theorthosis is sufficiently resilient to keep its three dimensional shape(generally as shown in FIG. 1) when not being worn by the patient.

The orthosis comprises an orthotic structure 10 which is comprised of afirst tubular section 12 and a second tubular section 14. The first andsecond tubular sections are contiguous, and in most instances the secondtubular section 14 will have been integrally formed with the firsttubular section 12. The first and second tubular portions are set at anangle to one another to provide, at least in use, a generally L-shapedinternal cavity 16 (FIG. 4) which is sized such that the orthosisaccepts and fits closely about the foot, ankle and lower leg of apatient (not shown) in use.

In a highly preferred arrangement the sock-like structure is formed notso that the first section is set perpendicular to the second, but sothat the structure exhibits approximately 3 to 10, preferably 5, degreesof dorsiflexion. This dorsiflexion drops to zero when the orthosis isbeing worn by a patient and the weight of their foot is applied to theorthosis during the swing through phase of their gait.

The orthotic structure 10 may be described as being generally“sock-like”, or in other words akin to a sock, in that when worn by apatient the second section 14 envelops a portion of the patient's lowerleg including the medial malleolus (the inside of the ankle) and thelateral malleolus (the outside of the ankle), and the first section 12envelops at least a portion of the plantar aspect of the foot (the soleof the foot) and at least a portion of the dorsal aspect of the foot(the front of the foot).

In the preferred arrangement (as depicted) the orthotic structure isconfigured so that the patient's toes and calcaneum (heel) are exposed.This is because we have found that an orthosis which exposes the heeland toes is significantly more comfortable for the patient to wear,whilst also giving the patient a greater sense of confidence whenwalking (particularly when barefoot) on a given surface due to the factthat their toes and heel can grip that surface. It will be appreciated,however, that the orthosis may instead be configured to envelop the toesand/or heel if desired.

As a further alternative for those patients with particularly sensitiveankles, the first and second sections may be configured so that thewalls of the first and second sections are thinned or include aperturesin those regions of the structure which would normally overlie themedial and lateral malleolae.

The resilience of the orthotic structure 10 is chosen, and may bevaried, in dependence upon the degree to which the patient suffers fromplantarflexion. In particular, the resilience of the orthotic structure10 is chosen to provide a resistance to plantarflexion that issufficient for correcting the particular degree of excessiveplantarflexion experienced by the patient who is going to be using theorthosis.

Variations in the resilience of a given orthotic structure 10 (as may berequired for patients experiencing a lesser or greater degree ofexcessive plantarflexion) may be effected by changing the material fromwhich the orthotic structure is formed, by changing the thickness of theorthotic structure, or by incorporating reinforcing means—such as aresilient rib—into the orthosis (or indeed by means of a combination ofthese).

As an illustrative example, the orthotic structure could includereinforcing means in the form of a resilient rib 16 (shown in ghost inFIG. 1) that extends partway along the dorsal aspect of the foot. Therib 16 could be formed integrally with the orthosis, or could beremovably insertable into a pocket provided on the dorsal aspect of theorthotic structure. The latter arrangement would be particularly usefulin that it would allow for the stiffness of the rib and/or the angle ofsupport (by inserting differently shaped ribs) to be changed if desired.The rib may be of the same material as the remainder of the orthoticstructure 10, or may be of a different—preferably moreresilient—material such as plastics, metal or carbon fibre.

The first 12 and second 14 tubular sections are formed of a resilientlyflexible material, and in the preferred embodiment this material is asilicone elastomer. Preferably the silicone elastomer has a Shore Adurometer of 30 to 80, preferably of 40 to 70, and most preferably of 50or 65.

The use of a resilient material for the orthotic structure 10 (andoptionally for the rib, if provided) is a fundamental departure from“under foot” or “over foot” devices of the type described above. Thesepreviously proposed devices recommended the use of a non-resilient, i.e.rigid, material. The primary advantage of using a resilient material asopposed to a rigid material is that the material can flex to storeenergy during certain phases of the patient's gait, and release thatenergy during other phases of the patient's gait (in particular theswing-through phase) to thereby actively assist the walking process as awhole, and dorsiflection in particular.

Dorsiflexion and plantarflexion of a foot is predominantly controlled bythe tibialis anterior muscle and tendon, and the structure of theorthosis functions to assist the operation of this muscle—in particularfor those patients who experience persisting foot drop resulting from aneurological impairment caused, for example, by trauma, disease orgenetics. This bio-mechanical function of the device of the invention isfundamentally different to so-called athletic support stockings, forexample those of the tubigrip® type, which provide no means forassisting the operation of the tibialis anterior muscle and tendon (toresist plantarflexion and assist dorsiflexion of a patient's foot), andare instead wholly concerned with resisting abnormal lateral movement ofthe foot.

As aforementioned, the orthotic structure 10 is closely fitted to thefoot and lower leg of the patient and as such may be configured toprovide a compressive force to the foot and lower leg of the patient. Ina preferred embodiment, the compressive force may be tailored to helptreat other conditions such as the effects and symptoms of venousinsufficiency, for example varicose veins. It is also conceivable fordifferent regions of the orthotic structure to provide differentcompressive forces. For example, the orthotic structure may exert agreater compressive force on the foot of the patient than on the anklein order to provide a pumping effect to assist blood flow to and fromthe foot.

Referring now to FIGS. 4 & 5, the second tubular section 14 of theorthotic structure is configured so that it can be opened to permit theorthosis to be put on by a patient. In this embodiment opening of thesecond tubular section 14 is achieved by configuring the second tubularsection so that it comprises a second part 20 that is arranged tooverlap a first part 18 when the orthosis 1 is in a closed positionfitted about the lower leg of the patient—the second part 20 beingmoveable (in a direction A indicated generally in FIG. 5) away from thefirst part 18 to open the second tubular section 14.

In the preferred arrangement, as depicted, the first part 18 comprises apart of the second tubular section 14 which extends generally from apart 22 of the orthotic structure 10 which overlies the medial malleoluswhen the orthosis is worn by a patient, and terminates at a line runninglongitudinally from an uppermost edge 24 of the second tubular section14 (i.e. that edge which is in the vicinity of the patient's lower legin use) to a lowermost edge 26 of the second tubular section 14 (i.e.that edge which is in the vicinity of the patient's calcaneum in use)generally midway between the part 22 of the second tubular section thatis arranged to overlie the patient's medial malleolus in use and a part28 (FIG. 4) of the second tubular section that is arranged to overliethe patient's lateral malleolus in use. The second part 20 comprises apart of the second tubular section 14 which extends generally from thepart 28 (FIG. 4) of the orthotic structure 10 which overlies thepatient's lateral malleolus to form a tab portion 30 which overlaps thefirst part 18 when the second tubular section 14 is closed. In thepreferred arrangement the tab portion 30 overlaps the first part 18(when the second tubular section 14 is closed) to an extent whereby thetab portion 30 terminates at an axial line 32 running longitudinallydown the second tubular section and terminating at or about that portion22 of the orthosis which overlies the patient's medial malleolus in use.

As depicted in FIGS. 4 & 5, in the preferred embodiment the orthosisincludes closure members 34 which are fixedly attached to theaforementioned tab portion 30 and which can be used—in a mannerdescribed in detail below—to secure the second tubular portion 14 in theaforementioned closed position about the lower leg of the patient. Inthe preferred arrangement two closure members are provided, but it willbe appreciated that a single closure member or more than two closuremembers may be provided if desired.

In the preferred embodiment, the closure members are fixedly attached tothe tab portion by means of tubular double-headed rivets 36, also knownas “speed rivets”, (or equivalent fixings) the like of which areavailable from Evans and Evans (Unit 24, Red Lion Business Park, RedLion Road, Tolworth, Surbiton, Surrey, UK), or Algeos (Sheridan House,Bridge Industrial Estate, Speke Hall Road, Liverpool, L249HB UnitedKingdom). Whilst it is undoubtedly the case that a variety of differentfixings will be immediately evident to those persons skilled in the art,speed rivets are nevertheless preferred as they permit the closuremember attachment stage of the orthosis production process to beaccomplished more quickly than if the closure members were, for example,to be sown onto the tubular section.

In the preferred embodiment where the tab portion 30 of the secondtubular section 14 overlaps the first part 18 it is preferred that theclosure members 34 are attached to the tab portion 30 in such a mannerthat the fixings 36 also overlap the aforementioned first part 18 of thesecond tubular section 14. This is highly advantageous as it means thatthe fixings do not bear on the patient's lower leg (where they couldcause discomfort) but instead bear upon the first part of the secondtubular section.

In the preferred arrangement, the closure members comprise a first stripof material 38 carrying on the outside 38 a thereof (i.e. the sidefacing away from the second tubular section) one part of a mechanicalhook and loop securing system (such as velcro®). A second strip ofmaterial 40 carrying on the inside 40 a thereof (i.e. the side facingtowards the second tubular section) the other part of the mechanicalhook and loop securing system is attached (for example sown onto) thefree end of the first strip of material 38. In a highly preferredarrangement the first strip of material 38 carries a set of hoops (andthe second strip 40 carries the hooks) so that the closure members donot interfere with any clothes that the patient might be wearing.

As mentioned above, the closure members are provided to enable thesecond tubular section to be secured in the aforementioned closedposition. To this end, the closure members can be wound (in thedirection B indicated in FIG. 4—i.e. in a continuation of the directionA (FIG. 5) in which the tab portion 30 may be moved to open the secondtubular section 14) round the periphery of the second tubular section 14until the hooks or loops on the second strip of material 40 overlie theloops or hooks on the first strip of material 38, whereupon the secondstrip of material 40 can be secured to the first 38 to secure the secondtubular section 14 in the closed position.

As an alternative, the closure members 34 could be affixed to the tabsection 30 in such a way that they are wound in the opposite direction(i.e. in a direction which would move the tab portion to close thesecond tubular portion) and then secured as aforementioned. However,such an arrangement is less preferred as pulling the closure member(s)in a direction which acts to close the tubular section 14 may encouragethe patient to overtighten the second tubular section about their lowerleg, perhaps to a point where the second tubular section is secured sotightly that it impacts adversely on the circulation in the patientslower leg and foot. This is particularly the case for those patients whohave suffered nerve damage and might not immediately be aware that theorthosis has been overtightened.

Whilst the above arrangement is preferred, it will be apparent that anumber of other alternatives are possible. For example, it is notnecessary for the closure members to be attached to the second tubularsection. The closure members could be detachable from the second tubularmember, and simply secured around it. The second tubular section 14, asdepicted schematically in FIG. 6, could also be provided with a numberof hoops 42 through which fully detachable closure members 34 could bethreaded and secured (as depicted).

As a further alternative, depicted schematically in FIG. 7, the closuremember could comprise a strip of material (not shown) that is fullydetachable from the orthosis and which carries hooks or loops of amechanical hook and loop engagement mechanism. The orthosis has twostrips of material 44 per closure member fixedly attached (for exampleby means of speed rivets 46 or equivalent fixings) to the second tubularsection 14—the first being attached to the outside of the aforementionedtab portion and the second being attached to the outside of a region ofthe aforementioned first part of the second tubular section which is notoverlapped by the tab portion when the second tubular section is closed.Each of the strips of material carry loops or hooks of the mechanicalhook and loop engagement mechanism, so that the detachable strip ofmaterial can be secured to each of the two attached strips of materialto hold the second tubular section in the closed position.

As a yet further alternative depicted schematically in a partly closedposition in FIG. 8, a strip of material 46 (carrying hooks or loops of amechanical hook and loop engagement mechanism on its outwardly face) maybe attached to the outside of a region of the second tubular section 14which is not overlapped by the tab portion 30 when the second tubularsection 14 is closed A second strip 48 of material, fixedly attached atone end to the tab portion 30 and carrying on its underside (i.e. theside facing the second tubular section) loops or hooks of the mechanicalengagement mechanism may then be secured to the strip of material 46fixedly attached to the second tubular section to secure the secondtubular section in the aforementioned closed position.

In another modification of the preferred embodiment depicted in FIGS. 4& 5, the closure member 34 does not necessarily need to comprise twostrips of material (38, 40) attached to one another. Rather, the closuremember could instead comprise a single strip of material provided withhooks or loops of the mechanical engagement mechanism on one side, andloops or hooks of the mechanism provided on the other.

As a further modification, the mechanical hook and loop closuremechanism could be replaced by another type of fixing—such as pressstuds for example.

In a further alternative arrangement not depicted in the drawings, thesecond tubular portion could be longitudinally split, with respectiveedges of the split being joined by a section of elastic material—theelastic material being sown or otherwise affixed to the resilientmaterial of the second tubular portion, and permitting the secondtubular section 14 to be opened for the insertion of a patient's footand lower leg. Any of the abovementioned closure members could then beprovided to secure the second tubular section around the patient's lowerleg (suitable modifications being made to account for the absence of atab portion).

As a further alternative arrangement it will be apparent to thosepersons skilled in the art that the tab portion 30 of the second tubularportion 14 need not overlap the first part 18. The second tubularportion 14 could simply comprise a longitudinal slit, one or moreclosure members being provided to bring opposed edges of the slittowards one another to close the slit and secure the second tubularsection about the lower leg of the patient. Such an arrangement, whilsteminently possible, is less preferred as the fixings used to attach theclosure member(s) to the orthosis would then be in contact with thepatient's lower leg.

Yet further configurations which permit the second tubular section to beopened will be apparent to those persons skilled in the art, but itremains the case that the configuration described in detail above withreference to FIGS. 1 to 5 is most preferred as the resulting orthosiscan more quickly be manufactured than an orthosis which included a stripof elastic material, for example.

As mentioned above, one advantage of the orthosis described herein isthat it can be manufactured much more quickly than the orthosisdescribed in our prior GB patent. Fabrication of an orthosis inaccordance with that prior patent necessitated the encapsulation ofvelcro® strips in the material of the orthosis to provide a means forclosing the insertion slit in the second tubular section. To manufacturean orthosis in accordance with the teachings provided herein all oneneed do is fixedly attach the closure member(s) to the second tubularsection for example by means of speed rivets, a much faster and muchmore robust alternative to the encapsulation of strips of velcro® in thebody of the orthosis.

The orthotic structure of either embodiment may be coloured so that itcan be matched to the skin colour of the patient (as can the closuremember(s)), and may be provided in a variety of different sizes andshapes. The orthotic structure may be manufactured by injection mouldingbut may alternatively be manufactured by milling (as described below)and subsequently building up layers of silicone elastomer upon asuitable cast (typically of a patient's foot and lower leg).

The orthotic structure, as mentioned above, may be manufactured from anumber of different resiliently flexible materials. Amongst these,silicone elastomer is a particularly preferred material. Two suitableelastomers are sold under the product names HCR9960 and MED4035 by NusilTechnology of 1050 Cindy Lane, Carpinteria, Calif., USA. Another familyof suitable elastomers are sold by Nusil Technology under the registeredtrademark VersaSil³®.

HCR9960 has a working time of approximately 1:2 hours and MED4035 has ashorter working time of approximately 3 to 4 hours, after which theelastomer cures. The elastomers are thermo-setting and are strainedthrough a 200 mesh screen to remove particulate contaminants.

The elastomers are supplied as A and B components which are preferablycombined in equal portions on a two roll mill, or other suitable device,prior to use.

A suggested sequence for blending the two components is to first softenpart B on the mill and then soften part A, after which an equal weightof part B should be added to part A and then thoroughly mixed. At thisstage, it is recommended to keep the temperature of the material as lowas possible so as to maximise the table life of the elastomer. Themixture may then be manually fitted to a plaster cast of a patient'sfoot, or more preferably supplied to injection moulding apparatus tomould a suitably shaped orthotic. Curing of the blended elastomer may beaccelerated by heat and can take from 3 to 4 hours. The cure may beinhibited by any ambient traces of organic rubbers and other substancesand thus it is important for the fabrication of the orthotic structureto be conducted in a thoroughly cleaned area.

The VersaSil³® family of elastomers include 3 base stocks which whenvulcanised produce tough, durable elastomers with Shore A durometers of30, 50 and 70, and the base stocks can be blended to produce elastomersof intermediate durometer. The three base stocks are compounded withCAT-40 and CAT-55-CAT-40 being an inhibitor, and CAT-55 being a platinumcatalyst.

Each series (i.e. 30, 50 or 70 durometer) is supplied as a three partsystem which must be compounded, for example on a two roll mill, priorto use. Elastomers of intermediate durometer can be produced by blending30, 50 or 70 durometer elastomers in a 1:1 ratio. For example, a 40durometer elastomer can be achieved by blending VersaSil³®30 andVersaSil³®50 in a 1:1 ratio mix.

To produce a given elastomer it is suggested to soften approximately 25%of the total required base stock on a cooled two roll mill. The entirerequired quantity of CAT-40 should then be added, and the resultingmixture milled until homogeneous. Whilst the base/CAT-40 mixture isturning on the mill, small increments of CAT-55 should be added untilthe entire required amount has been added. Next the remaining base stockshould added and milled. Once the elastomer has been produced, themixture may then be manually fitted to a plaster cast of a patient'sfoot or more preferably supplied to injection moulding apparatus tomould a suitably shaped orthotic structure.

Cure of the resulting mixture is accelerated by heat. For example, theelastomer will cure in a mould cross-section up to 0.075 inch (0.00195m) thick in less than ten minutes at 116° C. The vulcanisation rate canbe increased by increasing the cure temperature, and an optional postcure, such as four hours at 177° C. may be implemented if desired. Animportant point to note is that cure of the elastomer may be inhibitedby traces of amines, sulphur, nitrogen oxide, organo-tin compounds andcarbon monoxide. As such it is important for manufacture of the orthoticstructure to be conducted in a thoroughly clean environment.

The performance of the device described herein is expected to be atleast on a par with that provided by our previously proposed device (asdescribed in granted UK. Patent No. 2330309). This device was found toprovide a considerable improvement not only to the degree ofplantarflexion, but also to the walking speed and the effort involved inwalking (known as the Physiological Cost Index or PCI) of a group ofpatients. At an initial point in the study it was found that theorthosis provided an increase of roughly 10% in walking speed and areduction of roughly 2% in the PCI. At the end of the study, roughly sixmonths later, it was found that that same group of patients experiencedan increase in walking speed of roughly 20% and a reduction of roughly32% in the PC1 as compared to when they were initially without theorthosis. It is anticipated that the orthosis of the present inventionwill provide similar, and hopefully, better results.

We have also found that the orthosis of the present invention improvesthe patient's proprioception. When not wearing an orthosis as hereindescribed, patients tend to stumble when walking. However, when theorthosis is worn, the pressure exerted by the orthosis on the skinreceptors sends a message to the brain that helps the patient determinewhere the foot is in space. This in turn helps the patients to walkfaster and avoid stumbling.

It will be understood from the above that the orthoses herein describedprovide an effective means to tackle the problem of plantarflexion.Advantageously, and in addition to this function, the orthoses hereindescribed can significantly augment dorsiflexion during theswing-through phase of a patient's gait cycle. The principal reason forthis is believed to be that the orthotic structure (and resilient rib,if provided) store energy when compressed, and this energy is releasedduring the swing through phase of the patient's gait cycle. It isanticipated, therefore, that patients will not only find that theorthoses of the embodiments tackle the problem of plantarflexion butalso actively assist the walking process.

Whilst various preferred embodiments have been described above indetail, it will be apparent and should be noted that modifications andalterations may be made without departing from the spirit and scope ofthe invention as defined by the accompanying claims. It should also benoted that whilst particular combinations and permutations of featureshave been explicitly enumerated in the accompanying claims, the scope ofthe invention is not limited to those combinations and instead extendsto encompass any combination of features herein described irrespectiveof whether that particular combination of features has explicitly beenclaimed.

1. An ankle-foot orthosis for resisting plantarflexion of a patient'sfoot, the orthosis comprising: a resiliently flexible sock-like orthoticstructure formed of first and second tubular sections set at an angle toone another, wherein the second tubular section is capable of beingopened for insertion of the patient's foot and lower leg into respectiveones of said first and second tubular sections, the orthosis furthercomprising at least one closure member that can be passed round at leastpart of the periphery of the second tubular section and secured in placeto urge the second tubular section towards a closed position in whichthe second tubular section is closely fitted to the lower leg of thepatient.
 2. An orthosis according to claim 1, wherein the closure memberis located outside of the periphery of the second tubular section whenthe second tubular section is in said closed position.
 3. An orthosisaccording to claim 1, wherein the second tubular section has aconfiguration selected from one of the following configurations: (a) thesecond tubular section is longitudinally split to define an insertionslit, first and second edge portions of the slit being configured to liesubstantially adjacent one another when the second tubular section is inthe closed position; or (b) the second tubular section comprises firstand second edge portions, said second edge portion being separable fromthe first portion to permit the second tubular section to be opened andbeing configured to overlie the first edge portion when the secondtubular section is in the closed position.
 4. (canceled)
 5. An orthosisaccording to claim 3, wherein the at least one closure member is fixedlyattached to the orthotic structure.
 6. An orthosis according to claim 5,wherein the at least one closure member comprises a first closurefixedly attached to said second tubular section, and a second closurefixedly attached to the second edge portion, at least a free end of thesecond closure being securable to the first closure to secure the secondtubular portion in said closed position.
 7. An orthosis according toclaim 6, wherein said first closure and at least part of said secondclosure include appropriate complementary parts of a mechanical hook andloop securing system to permit the second closure to be secured to saidfirst closure.
 8. An orthosis according to claim 5, wherein the at leastone closure member comprises a strap fixedly attached at one end to oneof said first and second edge portions, said strap being configured tobe passed round the entire circumference of the second tubular sectionbefore being secured to itself to urge the second tubular sectiontowards the closed position.
 9. An orthosis according to claim 8,wherein at least parts of respective faces of said strap includeappropriate complementary parts of a mechanical hook and loop securingsystem to permit the strap to be secured to itself once it has beenpassed round the entire circumference of the second tubular section. 10.An orthosis according to claim 9, wherein the closure member comprises astrap fixedly attached by means of speed rivets to said second edgeportion, such that the speed rivets bear on said first edge portion whenthe orthosis is in the closed position and not on the patient's lowerleg.
 11. An orthosis according to claim 3, wherein the at least oneclosure member is at least partly separable from the orthotic structure.12. An orthosis according to claim 11, wherein said second tubularsection has configuration (a), and each said at least one closure membercomprises first and second closures fixedly attached to respective onesof said first and second edge portions, and a removable closure stripattachable to both of said first and second closures to secure thesecond tubular section in said closed position.
 13. An orthosisaccording to claim 11, wherein said second tubular section hasconfiguration (b), and the at least one closure member comprises a firstclosure fixedly attached to said second tubular section, a secondclosure fixedly attached to the second edge portion, and a removableclosure strip attachable to both of said first and second closures tosecure the second tubular section in said closed position. 14.(canceled)
 15. (canceled)
 16. An orthosis according to claim 11, whereinsaid at least one closure member is wholly removable from the orthoticstructure and is configured to be passed round the entire circumferenceof the second tubular section before being secured to itself to urge thesecond tubular section towards the closed position.
 17. An orthosisaccording to claim 16, wherein said second tubular section carries aplurality of loops through which a said closure member can be threadedto retain the closure member in a fixed position with respect to thesecond tubular section. 18.-21. (canceled)
 22. An orthosis according toclaim 1, wherein the orthotic structure is of silicone elastomer, saidsilicone elastomer having a Shore A durometer selected from the groupconsisting of: a Shore A durometer of 30 to 80, a Short A durometer of40 to 70, and a Short A durometer of 50 or
 65. 23.-31. (canceled)
 32. Anankle-foot orthosis for resisting plantarflexion of a patient's foot,the orthosis comprising: a resiliently flexible sock-like orthoticstructure formed of first and second tubular sections set at an angle toone another, wherein the second tubular section comprises first andsecond parts that are configured to be movable apart to open saidorthotic structure for insertion of the patient's foot and lower leginto respective ones of said first and second tubular sections, theorthosis further comprising at least one closure member separatelyformed from said resiliently flexible orthotic structure and coupled tosaid second tubular section in such a manner that said closure member isprovided with at least one free end, said at least one closure memberbeing configured to be passed circumferentially round the entireperiphery of the second tubular section prior to being secured to itselfto urge the second tubular section towards a closed position in whichthe second tubular section is closely fitted to the lower leg of thepatient.
 33. (canceled)
 34. (canceled)
 35. An orthosis according toclaim 32, wherein each said at least one closure member is configured tobe passed circumferentially round the periphery of said second tubularsection in such a manner that over-tightening of each said closuremember and hence over-tightening of said second tubular section, isprevented.
 36. An orthosis according to claim 35, wherein said firstpart of said second tubular section is arranged to overlie said secondpart of said second tubular section when said orthosis is in said closedposition, said first part of said second tubular section is arranged tobe moveable away from said second part in a first direction to open saidsecond tubular section, and each said closure member is arranged to bepassed in said first direction circumferentially round the periphery ofsaid second tubular section prior to being secured to itself to urge thesecond tubular section towards a closed position in which the secondtubular section is closely fitted to the lower leg of the patient. 37.An orthosis according to claim 36, wherein each said at least oneclosure member comprises a strip of material having a first face and asecond opposite face, wherein said first face is arranged to faceinwardly towards the periphery of said second tubular section and saidsecond face is arranged to face outwardly from the periphery of saidsecond tubular section when said closure member is secured about theperiphery of said second tubular section, at least part of said firstface including mechanical hooks of a complementary mechanical hook andloop closure and at least part of said second face includingcomplementary mechanical loops of a mechanical hook and loop closure.38. (canceled)
 39. A method of manufacturing an orthosis for resistingplantarflexion of patient's foot, the method comprising: preparing asilicone elastomer having a resilience which is appropriate forresisting the particular degree of excessive plantarflexion experiencedby the patient; applying the silicone elastomer to a three-dimensionalrepresentation of the patient's foot and lower leg to form a resilientsock-like orthotic structure formed of first and second tubular sectionsset at an angle to one another, said second tubular section beingcapable of being opened for insertion of the patient's foot and lowerleg into respective ones of said first and second tubular sections;allowing the silicone elastomer to cure; and fixedly attaching at leastone closure member to the orthosis, wherein the closure member ispassable, in use, round at least part of the periphery of the secondtubular section and securable in place to urge the second tubularsection towards a closed position in which the second tubular section isclosely fitted to the lower leg of the patient.